1. Field of the Invention
The present invention relates to a method for manufacturing a magnetic recording medium including a recording layer formed in a concavo-convex pattern.
2. Description of the Related Art
Conventionally, in a magnetic recording medium such as a hard disc, areal density has been largely improved by various types of development such as miniaturization of magnetic particles forming a recording layer, change of the material for the recording layer, and miniaturization of head processing. The further improvement of the areal density continues to be expected.
However, many problems including the limitation of the head processing, erroneous writing of data on adjacent tracks caused by spreading magnetic fields of the recording head, crosstalk, and the like are made apparent. Thus, the improvement of the areal density by the conventional development approach has reached the limit. Therefore, as candidates of a magnetic recording medium that enables further improvement of the areal density, a magnetic recording medium such as a discrete track medium or a patterned medium, in which a recording layer is formed in a predetermined concavo-convex pattern, has been proposed (see Japanese Patent Laid-Open Publication No. Hei 9-97419, for example).
On the other hand, when the surface of the medium is formed in a concavo-convex pattern, the flying height of a head slider may be unstable, thus degrading the recording and reproduction characteristics. Therefore, it is necessary to flatten the surface of the medium by depositing a non-magnetic material over the recording layer of the concavo-convex pattern to fill concave portions and then removing the excess part of the non-magnetic material above the recording layer.
As a technique for processing a recording layer in a concavo-convex pattern, dry etching can be used. As a technique for depositing a non-magnetic material, a deposition technique used in the art of semiconductor manufacturing, such as sputtering, can be used. In addition, as a technique for removing the excess part of the non-magnetic material above the recording layer to flatten the surface, a process technique used in the art of semiconductor manufacturing, such as CMP (Chemical Mechanical Polishing), can be used.
However, in the case of using CMP, it is difficult to precisely control the processed amount (thickness) on the order of several nanometers, for example, within a range of from about 1 to about 2 nm. Thus, the processing may not be performed sufficiently and therefore the non-magnetic material is left on the recording layer, or the processing may be performed excessively so as to remove a part of the recording layer. This degrades the magnetic characteristics of the recording layer.
Moreover, in the case of using CMP, slurry may react with the recording layer, thus degrading the magnetic characteristics of the recording layer. In addition, in the case of using CMP, cleaning and the like take large amount of time and cost in order to remove the slurry.
Furthermore, when CMP is combined with a dry process such as a process for processing the recording layer, transfer of an object to be processed and the like become complicated because CMP is a wet process. Thus, in this case, efficiency of the whole manufacturing process is lowered.